Installation and Field Work
Installation and Field Work
This domain tests hanging, assembling, sealing, and testing duct in the field, plus coordination with other trades. Field conditions rarely match the drawings exactly.
Core rules
- Supports: follow the project specification and code for hanger spacing and gauge. Rectangular duct needs trapeze or angle supports; round duct uses straps or saddles. Do not hang duct from sprinkler pipe, conduit, or other trades supports.
- Fire and smoke dampers: install listed dampers in rated assemblies, with access doors and correct sleeves; never cut or modify the damper frame.
- Sealing: match sealant to the SMACNA pressure class and seal class. Clean surfaces and seal joints, seams, and penetrations.
- Clearances: maintain code clearances to combustibles and electrical equipment.
- Testing: perform leakage tests before closing ceilings where required; then balance airflow with dampers.
Worked example
A 24 x 12 supply duct crosses a 1-hour rated wall. The correct detail is a listed fire damper in a sleeve, sealed to the rated assembly, with an access door on the accessible side and a fire-rated sealant. The reasoning: the wall fire rating must be maintained, and the damper must be inspectable and operable.
Traps
Supporting duct from another trades hangers; installing a fire damper where it cannot be accessed; sealing only the outside of a joint; and leaving flexible duct kinked or compressed.